A cytological basis for the separation of Geropogon from Tragopogon (Compositae: Lactuceae)

The single species ofGeropogon, G. hybridus (L.) Schultz-Bip., is sometimes submerged in the morphologically similarTragopogon. A comparative study of the karyotypes ofGeropogon andTragopogon sensu stricto clarified their relationship. The karyotype ofG. hydridus (2n=14) was compared with that ofT. dubius Scop. (2n=12). The karyotypes are distinct, offering a compelling reason to recognizeGeropogon as a separate genus.     

Chromosome numbers and taxonomic notes for Mexican coreopsis,sections electra and pseudoagarista (compositae: heliantheae)

Notes on morphology and chromosome numbers are given for several species of MexicanCoreopsis, most of which were poorly known prior to recent collections.Coreopsis parvifolia (sectionElectra) is a large, shrubby, octoploid (2n=112) species apparently restricted to a small area in Puebla. It andC. cuneifolia (a diploid with 2n=28) appear to be closely related but differ by a number of morphological features in addition to ploidy level. A first chromosome report forC. pringlei (sectionPseudoagarista) shows this rare species to be diploid (2n=26), a fact which is in agreement with the base number of the section, i.e.,x=13. Additional collections of the very rareC. rudis andC. mcvaughii show them to be similar yet distinct species. Chromosome determinations forC. petrophila from Nayarit and Durango agree with previous counts for Jalisco populations of the species, i.e., 2n=26. Considerable morphological variation exists within this species but no subspecific entities are recognized.     

Potential identification of chemical carcinogens in a viral transformation system

Chemical carcinogens from several diverse chemical classes i.e.; aromatic amines, polycyclic hydrocarbons, nitrosamines, hormonal derivatives, metals and direct alkylating agents cause a 6.2–60.5-fold increase in the frequency of murine sarcoma virus (MSV)-induced transformation in a normal rat kidney (NRK) cell system. Exogenous metabolic activation with a rat liver S-9 homogenate is required for expression of this activity by procarcinogens. Non-carcinogenic analogs of these compounds fail to cause significant increases in the transformation frequency either with or without prior metabolic activation. Iododeoxyuridine, a mutagen also does not cause enhancement of transformation. This system may serve as the basis for a rapid and quantifiable means of identifying chemical carcinogens while introducing a new model for the understanding of the interactions between oncorna-viruses and chemical carcinogens.     

The in vitro effect of indomethacin on basal bone resorption, on prostaglandin production and on the response to added prostaglandins

Mouse calvaria were maintained in organ culture without serum additives. Basal active resorption, as measured by ⁴⁵Ca and hydroxyproline release, was significantly inhibited to 74% control levels by indomethacin (1.4 × 10⁻⁷ M). Prostaglandin F and prostaglandin E₂ production, determined by radioimmunoassay, were both significantly lowered by this concentration of indomethacin. DNA, protein and hydroxyproline synthesis, as indices of cell toxicity, were unaffected by low concentrations of indomethacin, while concentrations of 1.4 × 10⁻⁶M inhibited protein synthesis (p<0.005). In the presence of indomethacin (1.4 × 10⁻⁷M) both PGE₂ and PGF_2α stimulated resorption in a dose-dependent manner, with PGE₂ being the more potent. Neither prostaglandin affected hydroxyproline synthesis at low concentrations, but PGE₂ had a marked inhibitory action at a higher concentration (10⁻⁶M). In combination, the effects of PGE₂ and PGF_2α showed no evidence of synergism or any antagonistic action. The study shows that in vitro calcium and hydroxyproline resorption in the unstimulated mouse calvaria are inhibited by indomethacin at concentrations measured in serum during human therapy. The decreased PGF and PGE₂ production associated with this decreased bone resorption in the presence of non-toxic concentrations of indomethacin would suggest a role for these prostaglandins in maintaining the basal resorption of cultured bone.     

The actions of opiates in the rat substantia nigra: An electrophysiological analysis

Single unit recording and micropressure ejection techniques were used to investigate the actions of opiates on dopaminergic and non-dopaminergic neurons in the rat substantia nigra. Systemic administration of morphine, 1 to 4 mg/kg, led to a naloxone-reversible increase in firing rate of all zona compacta dopaminergic (ZC) neurons examined (n=10). In a specifically defined subpopulation of non-dopaminergic nigral zona reticulata (ZR) neurons, systemically administered morphine led to a naloxone reversible decrease in activity (n=9). D-Ala²-d-leu⁵ (DADL)-enkephalin, when applied directly onto ZC neurons by micropressure ejection techniques, had no effect on their firing rate. In contrast, micropressure ejection of DADL enkephalin onto ZR neurons produced a decrease in firing rate which was blocked by systemically administered naloxone. Morphine sulfate applied by pressure ejection onto both ZC and ZR neurons produced mixed results which were not always blocked by naloxone. These results suggest that one of the mechanisms by which opiates increase dopaminergic neurotransmission is through disinhibition of dopaminergic neurons in the substantia nigra.     

Antibodies to muscarinic acetylcholine receptors in myasthenia gravis

IgG obtained from patients with myasthenia gravis block the specific binding of the muscarinic antagonists (³H)-N-methyl-4-piperidyl benzilate (4NMPB) and (³H)-Quinuclidinyl benzilate to rat brain muscarinic acetylcholine receptors. IgG obtained from healthy controls have a much smaller effect. The inhibitory effect of the myasthenic IgG increases linearly with immunoglobulin concentration and has no effect on the affinity of the muscarinic receptors towards (³H)-4NMPB (K_D = 0.7 ± 0.1 nM). This implies that the inhibition is probably due to the blocking of some of the muscarinic receptors by the myasthenic IgG, and not due to alteration in affinity of all the receptors. it remains to be established whether the presence of antimuscarinic receptor activity in the serum of myasthenic patients is of importance in the pathophysiology and diagnosis of myasthenia gravis.     

An unusual phenotypic expression of Hb-Leiden

After a boy of Mexican-American descent became jaundiced during treatment of a serious urinary tract infection with an oxidant drug, an extensive hematological examination was made. The important finding was the presence of Hb-Leiden to the extent of less than 3% or about a tenth of the usual percentage. Although inclusion bodies are present in the erythrocytes at all times, his hematological parameters have remained normal. The genetic basis for the unusually small amount of Hb-Leiden in the propositus may be due to the Hb-Leiden gene in an anti-Lepore configuration, that is, and Hb-Leiden gene in cis to the normal β and δ genes.     

Genetic control of hexokinase variation in insects

Hexokinase variation in insects appears to be under the control of a single locus in some species and under multiple-locus control in others. It is often difficult to distinguish the number of loci controlling hexokinase expression. Analysis of hexokinase electrophoretic patterns in six species of mosquitoes and five species of crickets, as well as a review of hexokinase variation in other insect species, is used to emphasize the importance of interspecific comparisons when making genetic inferences. Evidence is provided which adds support for multiple hexokinase loci in dipterans. Hexokinase control by multiple loci may be difficult to determine in some species because of tight linkage, disequilibrium, and/or posttranslational modification.This work was supported by NIH Grant AI 11132-09, NSF Grant DEB-7811188, and Yale Sesil Anonymous Funds.     

Oxidation-reduction potentials of respiratory chain components in Thiobacillus A2

(1) Cells of Thiobacillus A2 grown chemoautotrophically on thiosulfate or heterotrophically on succinate with oxygen contained b-, c-, o-, a- and a3-type cytochromes. The amount of cytochrome per mg of cell protein was much greater in thiosulfate-grown cells and differences in the relative concentrations of cytochromes were observed for the different growth conditions. (2) The half-reduction potentials at pH 7.0 (Em,7.0) and spectral maxima of c-, b-, a- and a3-type cytochromes were similar in cells grown aerobically with thiosulfate or with succinate as the growth substrate. (3) The half-reduction potential of the 'invisible', or high-potential copper, as determined from the potentiometric behavior of the carbon monoxide-reduced cytochrome a3 complex at pH 8.0, was 365 mV. (4) Reducing equivalents from thiosulfate appear to enter the respiratory chain at the cytochrome c level; however, studies in cell-free extracts were limited due to a loss in respiratory activity with thiosulfate as a substrate upon cell disruption.